I have the EXACT same problem!
I bought the car 5 days ago , with only 22000km.
2 days ago , I arrived to my destination, and all of a sudden the key wont switch to LOCK. and its just stuck there.
If I want to switch it to lock I'll have to jiggle and play with it for like 3-4 minutes. (totaly destroys my hand.).
I took it to a chevrolet shop and they said I have to replace the whole cylinder. ($342 work and parts). and thats without even checking. he just went in the car, saw it was stuck ,tried to take it out and thats it.
So what really should I do?
the car is automatic, is that really the problem? somthing with the stick not being enough "in" park?
Thanks in advance.